JP4588320B2 - Fuel processor with heat pipe cooling - Google Patents

Description

  The priority of US Provisional Application No. 60 / 311,459 (filed Aug. 11, 2001) is claimed, the contents of which are incorporated herein by reference.

  Fuel cells generate electricity from chemical oxidation-reduction reactions and have significant advantages over other types of power generation in terms of cleanliness and efficiency. Typically, fuel cells use hydrogen as the fuel and oxygen as the oxidant. The power generation is proportional to the consumption rate of the reactants.

  A significant drawback that prevents more widespread use of fuel cells is the lack of a widespread hydrogen structure. Hydrogen has a relatively low volumetric energy density and is more difficult to store and transport than the hydrocarbon fuels currently used in most power generation systems. One way to overcome this difficulty is the use of a reformer that converts hydrocarbons into a hydrogen-enriched gas stream that can be used as a feed for the fuel cell.

  Fuels based on hydrocarbons, such as natural gas, LPG, gasoline and diesel, require a conversion process in order to be used as a fuel source for most fuel cells. Current technology uses a multi-step process that combines the initial conversion process with several purification processes. The initial method is most often water vapor reforming (SMR), autothermal reforming (ATR), catalytic partial oxidation (CPOX) or non-contact partial oxidation (POX). The purification method usually consists of a combination of desulfurization, high temperature water-gas shift, low temperature water-gas shift, selective CO oxidation, or selective CO methanation. Alternative methods include hydrogen selective membrane reactors and filters.

  Despite the above work, there remains a need for a simple unit for converting hydrocarbon fuels into a hydrogen-enriched gas stream for use in connection with fuel cells.

  The present invention generally relates to an apparatus for converting a hydrocarbon fuel into a hydrogen-enriched gas, which produces a hydrogen-enriched gas in a cooperative relationship; a water gas shift reactor. And an apparatus comprising a selective oxidation reactor, wherein the temperature of the reactor bed is regulated by the use of heat pipes.

  In one such specific embodiment, the hydrocarbon reforming reactor includes a catalyst for reacting the fuel mixture under reforming conditions to obtain a hydrogen-containing gas mixture. The catalyst can be either an autothermal reforming catalyst, a steam reforming catalyst, or a combination thereof. The water gas shift reactor includes a catalyst for reacting the hydrogen-containing gas mixture under water gas shift reaction conditions to obtain an intermediate hydrogen-containing gas mixture with a substantially reduced carbon monoxide content. A selective oxidation reactor includes a catalyst for reacting the intermediate hydrogen-containing gas mixture under selective oxidation reaction conditions to obtain a hydrogen-enriched gas. In one specific embodiment, a heat pipe is used to transfer the heat generated in the selective oxidation reactor to preheat the hydrocarbon fuel into a high temperature hydrocarbon fuel, in which case the high temperature carbonization The hydrogen fuel becomes the hydrocarbon fuel feed for the hydrocarbon reforming reactor. The heat source for the reforming reaction heat pipe may preferably be an anode tail gas oxidizer for the fuel cell. The design and selection of the heat pipe used in the present invention may include a simple heat pipe, a variable conductivity heat pipe or a self-regulating variable conductivity heat pipe, or a combination thereof.

(Description of specific embodiments)
The present invention relates generally to an apparatus for converting hydrocarbon fuel to a hydrogen-enriched gas, wherein the temperature of the various reaction stages is regulated by the use of heat pipes. In a preferred embodiment, the apparatus and method described herein is a compact processor for obtaining a hydrogen-enriched gas stream from a hydrocarbon fuel for use in a fuel cell, comprising reaction temperature and heat integration. Relates to the compact processor achieved by the use of heat pipes. However, other possible uses are contemplated for the apparatus and methods described herein, including any use where a hydrogen-enriched stream is desired. Accordingly, although the present invention is described herein as being used in connection with a fuel cell, the scope of the present invention is not limited to such use.

  The reactor feed includes hydrocarbons, oxygen and water. The oxygen may be in the form of air, enriched air, or substantially pure oxygen. Water can be introduced as a liquid or vapor. The composition percentage of the feed component is determined by the desired operating conditions, as discussed below.

  The hydrocarbon fuel may be liquid or gas at ambient conditions as long as it can be vaporized. As used herein, the term “hydrocarbon” includes organic compounds having a C—H bond that are capable of producing hydrogen from a partial oxidation or steam reforming reaction. The presence of atoms other than carbon and hydrogen in the molecular structure of the compound is not excluded. Accordingly, fuels suitable for use in the methods and apparatus disclosed herein are (but not limited to) only fuels such as natural gas, methane, ethane, propane, butane, naphtha, gasoline, and diesel fuel. Rather, for example, alcohols such as methanol, ethanol, propanol and the like are also included.

  The effluent stream exiting the fuel processor of the present invention contains synthesis gas (hydrogen and carbon monoxide) and contains some water, carbon dioxide, unconverted hydrocarbons, impurities (eg, hydrogen sulfide) and inert components (particularly, If air is a component of the feed stream, it may also include, for example, nitrogen and argon.

  The reactors and structures disclosed herein can be made from any material that can withstand the operating conditions and chemical environment of the reactions disclosed herein, eg, stainless steel, Inconel. , Incoloy, Hastelloy and the like. The reaction pressure is preferably from about 0 to about 100 psig, although higher pressures can be used. The operating pressure of the reactor depends on the outlet pressure required by the fuel cell. For fuel cells operating in the 1-20 kW range, an operating pressure of 0 to about 100 psig is generally sufficient.

  In general, each exemplary embodiment of the present invention includes one or more of the following steps. FIG. 1 shows a general process flow diagram illustrating the steps involved in an exemplary embodiment of the present invention. Those skilled in the art will recognize that a certain amount of progressive order is required for the flow of reactants through the reactors disclosed herein.

Step A is a reforming step in which two different reactions can be performed. Formulas I and II are exemplary reaction formulas in which methane is considered as a hydrocarbon:

  The partial oxidation reaction (Formula I) takes place very rapidly until complete conversion of the added oxygen and is exothermic (ie generates heat). A high concentration of oxygen in the feed stream favors the partial oxidation reaction.

  The steam reforming reaction (formula II) is slow and endothermic (ie, consumes heat). A high concentration of water vapor favors water vapor reforming.

  Those skilled in the art will understand and appreciate that a combination of partial oxidation and steam reforming can convert the feed stream F into a synthesis gas containing hydrogen and carbon monoxide. In such cases, the oxygen to hydrocarbon ratio and the water to hydrocarbon ratio are characteristic parameters. These ratios affect the operating temperature and hydrogen yield.

  The operating temperature of the reforming process can range from about 550 ° C. to about 900 ° C., depending on the feed conditions and the catalyst. The present invention may be in any form including pellets, spheres, extrudates, monoliths, etc., or a thin wash over the surface of fins or heat pipes as described herein. A possible catalyst bed is used.

  Partial oxidation catalysts should be well known to those skilled in the art and are often, for example, platinum, palladium, rhodium and / or ruthenium on an alumina washcoat on a monolith, extrudate, pellet or other support. It is composed of noble metals such as Non-noble metals such as nickel or cobalt are also used. Other washcoats are listed in the literature, such as titania, zirconia, silica and magnesia. Many other materials, such as lanthanum, cerium and potassium, are listed in the literature as “promoters” (promoters, promoters) that improve the performance of partial oxidation catalysts.

  Steam reforming catalysts should be known to those skilled in the art and can include nickel with cobalt or an amount of noble metals such as platinum, palladium, rhodium, ruthenium and / or iridium. . The catalyst can be supported, for example, on magnesia, alumina, silica, zirconia, or magnesium aluminate, alone or in combination. Alternatively, the steam reforming catalyst can preferably include nickel supported on magnesia, alumina, silica, zirconia, or magnesium aluminate, alone or in combination, for example with an alkali metal such as potassium. Can be promoted.

  If step A is primarily an autothermal reforming step, then step B will generate a synthesis gas stream from step A from about 600 ° C to about 200 ° C, preferably from about 500 ° C to about 300 ° C, more preferably Cooling step to cool to a temperature of about 425 ° C. to about 375 ° C. to optimize the temperature of the syngas effluent for the next step. This cooling can be achieved by heat sinks, heat pipes or heat exchangers depending on the design specifications and the need to recover / recycle the heat capacity of the gas stream. In one exemplary embodiment, the condensing end of the heat pipe uses the feed stream as a heat sink when the feed stream enters the reactor, thereby preheating the feed stream, The reaction product gas is cooled. The heat pipe can be any suitable structure known to those skilled in the art, as discussed in more detail below. Alternatively or in addition, the cooling step B can be achieved by injecting additional feed components such as fuel, air or water. Water is preferred because it can absorb a large amount of heat when it vaporizes and becomes water vapor. The amount of component added is readily determined by those skilled in the art depending on the degree of cooling required.

  When the process A is mainly a steam reforming process, the process B is optional because the steam reforming process is endothermic. In such cases, heat is provided to the steam reforming process by a heat pipe having a condensation end incorporated into the catalyst bed. That is, in such exemplary embodiments, the catalyst bed serves as a heat sink for the heat pipe. The heat source in such exemplary embodiments can be an anode tail gas oxidizer or partial oxidation reactor, disclosed below as step G.

Step C is a purification step. One of the major impurities in the hydrocarbon stream is sulfur, which is converted to hydrogen sulfide by reforming step A. The processing core used in Step C preferably includes zinc oxide and / or other materials that can absorb and convert hydrogen sulfide, and supports (eg, monoliths, extrudates, Pellets and the like). Desulfurization is achieved by converting hydrogen sulfide to water according to Scheme III below:

  Other impurities, such as chloride, can also be removed. This reaction is preferably carried out at a temperature of about 300 ° C to about 500 ° C, more preferably about 375 to about 425 ° C. Zinc oxide is an effective hydrogen sulfide absorber over a wide temperature range from about 25 ° C. to about 700 ° C., providing great flexibility to optimize the process sequence by appropriate selection of operating temperatures. As in the prior art, the reaction temperature can be adjusted using a heat pipe, as will be apparent to those skilled in the art.

  The effluent stream is then sent to an optional mixing step D where water is added to the gas stream. The addition of water lowers the temperature of the reactant stream as it evaporates and supplies more water for the water gas shift reaction in step E (discussed below). Water vapor and other effluent components are passed through an inert material processing core, such as ceramic beads or other similar materials, which effectively mix the water and / or help vaporize the water. Can be mixed by. Alternatively, any additional water can be introduced with the feed and the mixing process can be rearranged to better mix the oxidant gas in the CO oxidation process G disclosed below.

に従って一酸化炭素を二酸化炭素に転化させる水性ガスシフト反応である。 Step E is represented by formula IV:

Is a water gas shift reaction that converts carbon monoxide to carbon dioxide.

  In this step, carbon monoxide that is harmful to the fuel cell is substantially removed from the gas stream and converted to carbon dioxide, which is generally considered an inert gas in the fuel cell. The concentration of carbon monoxide should preferably be reduced to a level acceptable by the fuel cell, typically below 50 ppm. In general, the water gas shift reaction can be performed at a temperature of 150 ° C. to 600 ° C., depending on the catalyst used. Under such conditions, most of the carbon monoxide in the gas stream is oxidized to carbon dioxide.

  Low temperature shift catalysts operate in the range of about 150 ° C. to about 300 ° C., such catalysts are copper, transition metal oxides supported on, for example, copper oxide or other transition metal oxides such as zirconia Or zinc supported on a refractory support such as silica, alumina, zirconia, etc., or platinum, rhenium, palladium, rhodium or gold supported on a suitable support such as silica, alumina, zirconia, etc. Including noble metals such as

  High temperature shift catalysts are preferably used at temperatures in the range of about 300 ° C. to about 600 ° C., such catalysts including transition metal oxides such as ferric oxide or chromium oxide. And optionally can include accelerators such as copper silicide or iron silicide. Further, where a high temperature shift catalyst is supported, noble metals such as supported platinum, palladium and / or other platinum group members are also included.

  The processing core used to perform this step can include a packed bed of high temperature or low temperature shift catalysts, or a combination of both high temperature and low temperature shift catalysts, eg, as described above. This process should be operated at any temperature suitable for the water gas shift reaction, preferably between 150 ° C. and about 400 ° C., depending on the type of catalyst used. Optionally, elements such as heat pipes can be placed in the processing core of the shift reactor to control the reaction temperature in the packed bed of catalyst. In such exemplary embodiments, the high temperature shift reaction is performed first, followed by the low temperature shift reaction. Controlling the reaction temperature is advantageous for the conversion of carbon monoxide to carbon dioxide. Furthermore, refining processing, such as desulfurization reaction (eg, Step C), provides separate steps for high temperature shift and low temperature shift between high shift conversion and low shift conversion, and high temperature shift step. And a desulfurization module between the low temperature shift process.

  Step F is a cooling step performed by a heat pipe in one embodiment. The heat pipe can be any suitable structure, as described below. The purpose of the heat pipe is to reduce the temperature of the gas stream to produce an effluent preferably having a temperature in the range of about 90 ° C to about 150 ° C.

  Oxygen is added to the process in step F. This oxygen is consumed by the reaction in step G described below. The oxygen can be in the form of air, reinforced air, or substantially pure oxygen. In this process, a heat pipe can be used to regulate the temperature of the gas, and the heat pipe is baffled and produces other turbulence-inducing structures that produce a mixture of oxygen and hydrogen-enriched gas. Can be designed with fins.

Process G is an oxidation process in which residual carbon monoxide in the effluent is substantially converted to carbon dioxide. The two reactions are performed in Step G: the desired oxidation of carbon monoxide (Formula V) and the undesired oxidation of hydrogen (Step VI) as follows:

  The processing is performed in the presence of a catalyst for the oxidation of carbon monoxide, and the catalyst can be in any suitable form, such as pellets, spheres, monoliths, and the like. Carbon monoxide oxidation catalysts are known and typically include noble metals (eg, platinum, palladium) and / or transition metals (eg, iron, chromium, manganese) and / or compounds of noble metals or transition metals, In particular, oxides are included. A preferred oxidation catalyst is platinum on an alumina washcoat. The washcoat can be applied to monoliths, extrudates, pellets or other carriers. Additional materials such as cerium or lanthanum can be added to improve performance. Several other formulations have been cited in the literature by several practitioners claiming performance superior to alumina-supported rhodium catalysts. Ruthenium, palladium, gold and other materials are listed in the literature as being effective for this use.

  The preferential oxidation of carbon monoxide is favored by low temperatures. Since both reactions generate heat, a heat pipe can be placed in the reactor to remove the heat generated in the process. The operating temperature of the process is preferably maintained within the range of about 90 ° C to about 150 ° C. In this way, those skilled in the art will understand that this process can serve as a substantial heat source and therefore integrate with other processes that are endothermic, eg, steam reforming in process A, using a suitable heat pipe. It should be recognized that it can be done.

  Step G preferably reduces the carbon monoxide level to less than 50 ppm, which is a suitable level for use in a fuel cell, but those skilled in the art will recognize that the present invention reduces higher and lower levels of carbon monoxide. It should be recognized that it can be applied to the production of hydrogen-enriched products having.

  The effluent P exiting the fuel processor is a hydrogen enriched gas containing carbon dioxide and other components that may be present, such as water, inert components (eg, nitrogen, argon), residual hydrocarbons, etc. is there. The product gas can be used as a feed for a fuel cell or for other applications where a hydrogen enriched feed stream is desired. Optionally, the product gas can be sent to further processing, for example to remove carbon dioxide, water or other components.

  Although general methods have been described, those skilled in the art should recognize and understand that a major challenge with regard to the economic viability of the fuel processor is low cost thermal management. Challenges to overcome include control of reaction temperature in the catalyst bed; rapid heat addition to the bed for rapid start-up; heat removal in such a way as to maintain a constant bed temperature; economically feasible Commercial production of fuel processors at cost; as well as other challenges that are well known to those skilled in the art.

  A heat pipe is a device used to quickly remove heat and maintain the temperature at an accurate setting. Simple and inexpensive copper / water heat pipes can be used in the temperature range of the fuel processor zinc oxide (step C), water gas shift (step E) and partial oxidation (step G) catalyst beds. If the temperature exceeds 500 ° C., for example at the outlet of the autothermal reforming catalyst (Step A), this high temperature requires the use of other materials, such as stainless steel / sodium heat pipes. To do.

  Those skilled in the art understand that heat pipes, also known as thermo-siphons, are devices that are widely used to transport high-speed heat flows at negligible temperature drops, that is, devices that have inherent ultra-high thermal conductivity. And should recognize. A great variety of heat pipes are disclosed in the literature and should be known to those skilled in the art. Selection of an appropriate heat pipe will determine whether the controlled reaction will serve as a heat sink or a heat source; the desired temperature range; the acceptable range of temperature changes accepted by the reaction; the efficiency; the cost; Depends on several factors, including other factors that are obvious to the vendor. To subsidize such skilled technicians, the following descriptions of several types of heat pipes are provided below. However, it should be understood that many types of heat pipes exist and can be used within the scope of the present invention.

  Referring now to FIG. 2, the heat pipe 210, in its simplest and most popular “generic” form, also referred to as a “constant conductivity heat pipe”, is a saturated thermal equilibrium working fluid 214 ( Including a general pipe-shaped closed pressure vessel 212 containing liquid and vapor). External heat is input to the evaporator section 216 and heat is removed from the condenser section 218 to an external heat sink (not shown). The evaporator section 216 and the condenser section 218 are connected by a vapor flow rate and an internal capillary wick 222. The working fluid 214, such as ammonia or water or other fluid, absorbs its phase-change “heat of vaporization” as it evaporates in the evaporator section 216 and condenses as shown by the dash arrow 221. Flows to the condenser section 218 and condenses to give its heat to the 212 wall of the heat pipe. The working fluid is then returned to the evaporator section 16 in liquid form by capillary pumping in the wick 222. One useful heat pipe material is aluminum because it is easily extruded to have a fine channel integral wick in the vessel wall. However, heat pipes can also be made from other metals, including copper and stainless steel.

  The general heat pipe described above is passive; that is, its conductivity is essentially constant, said heat pipe modulates the conductivity and "actively" controls the temperature. There are no features. Other forms of heat pipes have features that produce active temperature control or diode action, examples of which are shown in FIGS. 3a and 3b. One form of “active control” heat pipe 320 is referred to as a “variable conductivity” heat pipe. The variable conductive heat pipe eliminates a controlled portion of the working fluid 314 in the condenser 318 depending on the amount of non-condensable gas 329 contained and condenses containing the working fluid 314. The portion of vessel 318 is thermally inactive. Non-condensable gas is stored in a reservoir 328 (ie, non-condensable gas reservoir) connected to the end of the condenser and is partially removed from the reservoir 328 into the condenser 318. As shown in FIG. 3a, this occurs when heated by an electric heater 332 on the reservoir 328 wall. As shown in FIG. 3b, this occurs by controlling the heat that is distributed by the fins 330 to a cooling fluid (not shown) such as air or coolant. The amount of noncondensable gas is primarily a function of the temperature of the reservoir 328. In FIG. 3a, the amount is controlled by a thermostat, or a temperature sensor 334 on the evaporator 316 controls the operation of the non-condensable reservoir heater 332 and thus the temperature of the evaporator 316. In FIG. 3 b, the amount is controlled by controlling the flow rate and speed of the cooling fluid (not shown) on the cooling fins 330. The variable conductive heat pipe 320 works very well, is reliable and predictable. The capacity of the non-condensable gas reservoir 328 is proportional to the condenser 318 length of the variable conductive heat pipe 320; thus, the condenser 318 length is the capacity, mass associated with the non-condensable gas reservoir 328. And usually limited by the power limitation of the heater 332 and not defined by the actual condenser 318 length requirements based on the required radiator area.

  Several variable conductive heat pipes 320, for example as shown in FIGS. 3a and 3b, work very efficiently to maintain the constant temperature of the evaporator. For example, the variable conductivity heat pipe condenser 318 can have a full 0-100% effective range corresponding to a narrow evaporator temperature zone, on the order of 1 ° C or 2 ° C.

  A self-regulating variable conductive heat pipe is disclosed in US Pat. No. 4,799,537, the contents of which are incorporated herein. As described in the patent, a self-regulating heat pipe is a sealed hollow casing; a quantity of vaporizable heat transfer fluid in the casing; a quantity of non-condensable in the casing. Gas; an inflatable first reservoir volume with an opening (the first reservoir being acted on by pressure means within the casing to which heat is applied and resists expansion of the first reservoir volume; Disposed in the evaporator region, in which case the pressurizing means is a second reservoir filled with non-condensable gas and the first reservoir volume is enclosed in the second reservoir); It includes conduit means having one end coupled to the opening and the other end opening (from which heat is removed) into the condenser region of the heat pipe. Next, FIG. 4 illustrates a simplified cross-sectional view along the axis of a self-regulating heat pipe of the type described in US Pat. No. 4,799,537, in which case the heat A pipe 410 encloses the non-condensable gas first reservoir 412 and the second reservoir 414.

  The heat pipe 410 is conventionally comprised of a sealed casing 416 with a thin tube wick 418 that covers the inner wall of the casing 416. During operation, one end of the heat pipe 410 is the evaporator region 420 and heat is applied to the region 420 and the other end is the condenser region 422 from which heat is removed. If the heat pipe 410 is emptied and only vaporizable working fluid is loaded from the fill tube 424, this functions as a conventional heat pipe.

  However, if a non-condensable gas, such as nitrogen, is also loaded into the heat pipe 410, the heat pipe 410 functions somewhat differently. As is well understood in the art, the movement of the working fluid vapor removes non-condensable gas to the condenser region 422 of the heat pipe 410, where it is recovered and occupied by the gas. This prevents the heat pipe part from functioning as a heat pipe. Indeed, a boundary 426 is formed between the heat pipe volume containing non-condensable gas and the heat pipe volume not containing.

  A second reservoir 414 having a non-expandable structure is disposed in the evaporator region 420. The second reservoir encloses the first reservoir 412, the opening of the first reservoir 412 is coupled to the conduit 428 and is maintained in place by the clamp 430. The end of conduit 428 remote from first reservoir 414 opens into the interior of heat pipe 410 near the end of condenser region 422 furthest from evaporator region 420. The open end of conduit 428 is positioned well within the non-condensable gas containing region of the heat pipe. Thus, during nominal operation, non-condensable gas fills conduit 428 and partially expands inflatable first reservoir 412. This expansion is suppressed and limited by the pressure of the non-condensable gas loaded into the second reservoir 414 from its fill tube 432.

  The pressure of the gas in the second reservoir 414 determines the temperature control point of the heat pipe, and this pressure is one of the design parameters. The pressure of the gas in the second reservoir 414 should be the same as the vapor pressure of the heat transfer fluid in the heat pipe at the nominal operating temperature.

  Once the pressure of the gas in the second reservoir 414 is determined, a pressure balance is achieved between the second reservoir 414 and the gas and vapor mixture in the expandable first reservoir 412, which is the working fluid vapor. A boundary 426 is located where pressure and the pressure of the mixture of vapor and non-condensable gas are equally even.

  It is disclosed that the automatic control phenomenon functions as follows. If the condition seeks to increase the temperature of the evaporator region 420, the vapor pressure of the heat transfer fluid tends to increase. This pushes the boundary 426 away from the evaporator region 420, thus activating the larger surface of the heat pipe 410 in the condenser region 422 to provide more cooling and to increase the temperature rise in the evaporator 420. Restrict.

  The movement of the boundary 426 is adjusted from the boundary 426 by the expansion of the first reservoir 412 that is effectively present at the opposite end of the composite gas vapor zone, so only a slight resistance is encountered. The expansion of the first reservoir 412 itself is almost in resistance because its movement is limited only by the gas pressure in the second reservoir 414, which is nominally the same as the vapor pressure of the heat transfer fluid as described above. Absent. Therefore, an increase in the capacity of the first reservoir 412 limits the temperature increase in the evaporator region 420, and a decrease in the capacity of the first reservoir 412 also occurs to limit the temperature decrease in the evaporator region 420.

  This feedback system is a constant temperature since the non-condensable gas in the second reservoir 414 and the first reservoir 412 is essentially the temperature of the evaporator region 420, thus eliminating any temperature change that affects the pressure. It is subsidized by the fact that. Further, since the temperature of the gas is approximately the same as the highest temperature in the system, no vapor condensation occurs in the expandable first reservoir 412.

  Self-regulating heat pipes of the type described above are composed of copper with water as the working fluid and with an inflatable first reservoir constructed from an aluminized plastic film such as MYLAR®. Has been tested with a heat pipe. The disclosed embodiment shows that the heat pipe evaporator temperature is only 1. from the set point temperature of 36.1 ° C., with a change in heat sink temperature ranging from minus 0.23 ° C. to plus 29.4 ° C. It is reported that it showed excellent self-regulation because it changed by 15 ° C. On the other hand, more conventional heat pipes, including fixed wall non-condensable gas reservoirs, can be expected to have a change in evaporator temperature that is about four times greater.

  One exemplary embodiment of the present invention is shown in FIG. 5 as a horizontal cross-sectional view of a reaction chamber 502 in which a helical heat pipe 504 is disposed. The helical shape of the heat pipe allows the addition of a catalyst (not shown) such that heat transfer from the catalyst to the helical heat pipe occurs. A heat transfer block 506 is used to ensure reactor integrity. The reactor end of the heat transfer block is in thermal communication with the helical heat pipe. The exterior side of the heat transfer block is in thermal communication with a second heat pipe 508 that dissipates the heat of the heat transfer block. As shown, the condenser end of the second heat pipe has a heat dissipating fin.

  Another exemplary embodiment of the present invention is shown in FIG. 6, which shows a small fuel processor 600 as a schematic cross-sectional view. As shown, the anode tail gas oxidizer 602 preheats the feed gas (F) and is used as the first heat source for the reformer section (Step A). Although the reformer section can be designed to be an autothermal reformer, it is preferred that the reformer section be a steam reformer because of the close proximity of the anode tail gas oxidizer. The hydrogen-containing gas from reformer section 604 enters the hydrogen sulfide / zinc oxide reactor (Step C) and is cooled by ambient heat pipe 612. The hydrogen-containing gas then proceeds to the water gas shift reaction section 608 (Step E) where the CO content is substantially reduced. The hydrogen-containing gas proceeds into a partial oxidation reactor 610 (Step G) that is cooled by heat pipes or heat fins 614. The product hydrogen enriched gas P exits the reformer and is preferably ready for use in a fuel cell.

  A third exemplary embodiment of the present invention is shown in FIG. For example, published U.S. Patent Application No. US2002 / 0083646A1; US2002 / 0094310A1; US2002 / 0098129A1; US2002 / 0090334A1; US2002 / 0090326A1; US2002 / 0088740A1; US2002 / 0090327A1; US2002 / 0090328A1. FIG. 4 shows a horizontal cross-sectional view of a heat pipe used in place of a conventional fluid-based heat exchanger of a small fuel processor 700, as disclosed in US Pat. Next, in FIG. 7, the reactor 702 has heat pipes (704 and 706) having an evaporation end 704 and a condensation end 706. As shown, the evaporation end 704 (i.e., heat source) of the heat pipe is contained within the reactor and the condensation end 706 (heat sink) is external to the reactor. Those skilled in the art will recognize and understand that both ends are interchangeable, such that the interior of the reactor is a heat sink. Such a case is the case of a reactor in which an endothermic reaction is performed, such as steam reforming, for example. The heat fins 708 have a dual functional role of supporting the catalyst and further promoting heat transfer. In one exemplary embodiment, a heat pipe is used to preheat the feed gas prior to entering the steam reformer. One skilled in the art can further connect the illustrated heat pipe condenser section 704, as shown in FIG. 8, to a similarly shaped finned heat pipe in other sections of the fuel reformer. I should understand that too. As shown in the side cross-sectional view, the fuel reformer 800 encloses both the condensation section 802 and the evaporation section 804 of the heat pipe. Both sections are connected together by one or more thermal conduits 806 or a second heat pipe.

  Those skilled in the art will further recognize that we consider that the outer surface of the heat pipe and / or the fins can be coated with catalyst and / or catalyst particles. It has been reported that fins can be coated relatively easily with ceramic catalysts. The idea shown in FIG. 7 is to coat the fin with a catalyst by passing the heat pipe through the fin. Utilizing this, in addition to cooling the exothermic reaction, it is also possible to heat a catalyst bed that requires external heat to cause a reaction such as steam reforming, for example. The coating process requires that the particulate catalyst be washcoated on the surface of the fin immediately after the heat pipe is manufactured. This device maximizes the surface area of reaction and heat exchange on the heat pipe by mounting finned extrusions on the heat pipe and coating these fins with a catalyst. Is. FIG. 7 shows a heat pipe “shaped in a fork shape”, but it is also conceivable that the heat pipe may be helical as shown in FIG. Other similar variations to increase the surface area of the heat pipe should be obvious to those skilled in the art.

  Although the apparatus and method of the present invention have been described with reference to preferred embodiments, it will be apparent to those skilled in the art that changes can be made to the processes described herein without departing from the concept and scope of the present invention. Will. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the scope and concept of the invention.

With reference to the attached drawings, the explanation is as follows:
FIG. 1 shows a simple process flow diagram of one exemplary embodiment of the present invention. FIG. 2 shows a simple heat pipe that can be used in an exemplary embodiment of the invention. Figures 3a, b show a variable conductivity heat pipe, as can be used in an exemplary embodiment of the invention. FIG. 4 shows a self-regulating variable conductive heat pipe that can be used in an exemplary embodiment of the present invention. FIG. 5 shows in horizontal cross section a heat pipe that can be used in an exemplary embodiment of the present invention. FIG. 6 illustrates in side cross-sectional view a heat pipe used for thermal management integration within a fuel reformer, such as can be used in an exemplary embodiment of the present invention. FIG. 7 shows a finned heat pipe in a horizontal cross-sectional view that can be used in an exemplary embodiment of the present invention. FIG. 8 shows in side cross-sectional view a heat pipe used for the integration of thermal management within a fuel reformer, as can be used in an exemplary embodiment of the present invention.

Claims (8)

An apparatus for converting a hydrocarbon fuel into a hydrogen enriched gas for a fuel cell,
A hydrocarbon reforming reactor comprising a catalyst for reacting the fuel mixture under reforming conditions to obtain a hydrogen-containing gas mixture;
A water gas shift reactor comprising a catalyst for reacting the hydrogen-containing gas mixture under water gas shift reaction conditions to obtain an intermediate hydrogen-containing gas mixture with reduced carbon monoxide content; and selecting the intermediate hydrogen-containing gas mixture A selective oxidation reactor comprising a catalyst for reacting under selective oxidation reaction conditions to obtain a hydrogen-enriched gas,
The hydrocarbon reforming reactor bed, water gas shift reactor bed, and selective oxidation reactor bed temperatures are controlled by the use of heat pipes,
A heat pipe for transferring the heat generated in the selective oxidation reactor to preheat the hydrocarbon fuel into a high temperature hydrocarbon fuel, wherein the high temperature hydrocarbon fuel is directed to the hydrocarbon reforming reactor; Becomes a hydrocarbon fuel feed,
The reforming reaction is steam reforming, the reforming reaction serves as a heat sink for a heat pipe;
The heat pipe is a copper / water heat pipe or a stainless steel / sodium heat pipe;
And further comprising a desulfurization reactor comprising a catalyst for reacting the hydrogen-containing gas mixture under desulfurization conditions to obtain a desulfurized hydrogen-containing gas mixture, wherein the desulfurized hydrogen-containing gas mixture is supplied to the water gas shift reactor. Of hydrogen-containing gas mixture feeds,
The above device. The apparatus of claim 1, wherein the heat pipe is selected from a simple heat pipe, a variable conductivity heat pipe, or a self-regulating variable conductivity heat pipe. The apparatus of claim 1, wherein the heat pipe is a self-regulating variable conductive heat pipe. The hydrocarbon fuel of claim 1, wherein the hydrocarbon fuel is selected from the group consisting of natural gas, methane, ethane, propane, butane, liquefied petroleum gas, naphtha, gasoline, kerosene, diesel, methanol, ethanol, propanol, and combinations thereof. apparatus. The apparatus of claim 1, wherein the hydrogen-enriched gas contains less than 50 ppm of carbon monoxide. The apparatus of claim 1, further comprising an anode exhaust gas oxidizer comprising a catalyst for reacting unconverted hydrogen from the fuel cell under oxidizing conditions to produce a hot anode exhaust gas oxidizer effluent. 7. The apparatus of claim 6, wherein the hot anode exhaust gas oxidizer effluent is heat integrated with a hydrocarbon reforming reactor using a heat pipe. The apparatus of claim 1, wherein the heat pipe maintains a constant bed temperature within at least one of the hydrocarbon reforming reactor, the water gas shift reactor, and the selective oxidation reactor.

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